Sanitary double wall bag



Oct. 18, 1966 w CALVERT SANITARY DOUBLE WALL BAG Filed April 12, 1963 INVENTOR. WILLIAM L.CALVERT ATTORNEY United States Patent 3,279,966 SANITARY DOUBLE WALL BAG William L. Calvert, Westfield, N.J., assignor to Union Carbide Corporation, a corporation of New York Filed Apr. 12, 1963, Ser. No. 272,647 6 Claims. (Cl. 156-152) This invention relates to sanitary double wall bags, and more particularly to a method for producing sanitary, spouted, double walled plastic film bags for use as containers for food products such as milk.

Interest in the use of plastic film bags as liners in pasteboard board boxes for the shipment of milk and other food products has grown rapidly, particularly with the advent of processes which inherently form continuous tubular films, with sterile internal surfaces. United States Patent Number 2,461,975, to Fuller, for example, discloses a process for producing continuous seamless tubing from a melt of a thermoplastic organic material wherein the operation at temperatures at least equal to the melting point of the film material, inherently sterilizes the resultant product. The internal sterility of the tubular film is preserved by flattening the continuous tubing and thus precluding the penetration of air into the tubing.

The preservation of -the internal sterility of the bag and the automation of the bag-making process is seriously complicated by the step of attaching a filling and/or dispensing spout to the bag.

While double wall bags have shown generally superior performance in the packaging field, the production of double wall bags further complicates the problems of automation and preservation of sterility.

It is, therefore, an object of the present invention to provide a process for attaching a spout to a double wall bag which is capable of being carried out automatically.

It is a further object of the present invention to provide a process for forming a sterile, double wall bag which is capable of being carried out automatically.

According to the present invention a process for forming sterile double wall bags is provided, which includes forming a plurality of pairs of contiguous sheets, each of which has an outer surface and an inner, sterile surface in contact with an inner sterile surface of a contiguous sheet.

The plurality of pairs of contiguous sheets are advantageously formed by continuously melt extruding a plurality of seamless tubings, continuously withdrawing each of tu'bings from the point of extrusion, flattening of the tubing at a point spaced from the point of extrusion, initiating and maintaining an isolated bubble of a gaseous medium in the section of each of the tubings between the point of extrusion and the point of flattening, continuously withdrawing each of the tubings from the point of flattening and cutting the opposing edges of each of the flattened tubings. Each of the sheets in the pairs of contiguous sheets thus produced, has an outer surface and an inner sterile surface in close contact with a second inner sterile surface of a contiguous sheet.

Within a sterile environment, each of the sheets is withdrawn from contact with the sheet with which it is contiguous and the outer surface of at least one sheet in each of the pairs of sheets is brought into contact with a surface of another sheet thus transforming an inner surface into an outer surface and forming pairs of sheets, each having an outer sterile surface. While within a sterile environment, spouts can be added to one or more of the pairs of sheets and then the outer sterile surface of one pair of sheets brought into contact with an outer sterile surface of another pair of sheets. The peripheral edges of the two pairs of cont-acting sheets are sealed, as

for example, by means of heat, in order to form a double wall bag having a sterile interior zone.

In this manner, a double film container is formed which is sterile on the inside, but yet has heat sealed ends and an integral spout or similar opening or pouring means.

Other advantages of the invention will be appreciated and the invention will be better understood from the following specification wherein the invention is-described by reference to the embodiments illustrated in the accompanying drawings wherein:

FIGURE 1 is a diagrammatic, side elevation, showing the process of the present invention,

FIGURE 2 is a fragmentary, side elevation, showing the step of transforming inner surfaces into outer surfaces, and

FIGURE 3 is a fragmentary, side elevation, showing a modification of the step of FIGURE 2.

The process involves basically, the formation of a double walled plastic film bag having a sterile interior zone by peripherally heat sealing two pairs of sheets.

While film forming plastics in general can be employed in the process of the present invention, those which are capable of being melt extruded in the form of a tube and are capable of being heat sealed are preferred. Illustrative of plastics which can be employed are polymers and copolymers of polyolefins such as polyethylene, polypropylene, polystyrene, and poly(vinyl chloride), nylons, regenerated cellulose, the cellulosic derivatives and rubber hydrochloride.

The process as shown in FIGURE 1, employs a first pair of continuous sheets 10, which have a sterile surface 12, and a second pair of continuous sheets 11. which have a sterile surface 13.

The sheets can be formed by any process which is capable of producing a pair of contiguous sheets having sterile, inner contacting surfaces. The process disclosed by Fuller, in United States Patent 2,461,975 has been noted to produce a thermoplastic tubing having a sterile interior surface. Advantageously, the tubing formed by the Fuller process, can be flattened and the edges of the flattened tubing cut, as for example, by trimming off the curved edges, thus formed a pair of contiguous sheets. The sheets thus formed will have the requisite sterile contacting surfaces. Maintaining the pair of sheets in contact is sutlicient to preserve the sterility of the inner surfaces.

The edge trimming operation would appear to open the tube and expose the interior of the tube to contamination. The fact, however, is that the mere blocking together of the sheets precludes the penetration of air until such time as the sheets are mechanically peeled apart. The blocking of the sheets is readily produced by passing the tubing between a pair of squeeze rollers and producing a firm contact between the two halves of the flattened tubing. The preservation of the blocked condition of the sheets is assured after the cutting operation, by simply winding the sheets onto a roll and thus preventing the sheets from peeling apart. Rigid sanitary controls are not necessary to maintain the continued sterility of the interior surfaces of the tubing during a period in which blocked sheets are stored and shipped.

The Fuller process is thus seen to have the advantage of not requiring sanitary precautions during the film making or storing operations, due to the sterilization inherent in the tubing formation operation and the inherent preclusion of air penetration into the flattened tubing, and the maintaining of the sheets in contact, after the tubing has been cut, is suflicient to preserve the sterility of the inner surfaces.

As shown in FIGURE 2, a pair of sheets 21 and 22 have their inner sterile surfaces 23 and 24, respectively, in firm I? contact. While a sterile environment is maintained the sheets are drawn apart at 23, and one of the sheets 21, is brought around to the outer side 25, of the other sheet 20. The surfaces 25 and 26, which previously served as outer surfaces, are thus transformed into inner contacting surfaces and conversely, the inner, sterile, contacting surfaces 23 and 25 are transformed into outer sterile surfaces.

As shown in FIGURE 3, a roll of sheets 40 consisting of a pair of sheets 31 and 32 may be separated at 38, and then brought into contact with sheets 41 and 42. Inner sterile surfaces 35 and 36 can be transformed into outer surfaces by bringing the outer surfaces 33 and 34, or the sheets 31 and 3 2 into con-tact with the corresponding sheets 41 and 42. The sterile surfaces 35 and 36, of the first pair of sheets 31 and 32 serve as the inner surfaces of the sterile bag which the second pair of sheets 41 and 42 serves as the outer walls of the bag. Therefore, the second pair of sheets need not have any sterile surface, but rather, one or both of the sheets 41 and 42 can be formed by any conventional operation which is capable of producing a single layer film preferably in continuous form.

As shown in FIGURE 1, a pair of sheets is fed from a roller 10, to a spout attaching apparatus. The sheets have a first lower surface 12 which must have the desired degree of sterility. The pair of sheets may comprise sheets formed by cutting the edges of :a flattened tubing. In this case, a reversing operation, such as seen in FIG- URE 2, is necessary as previously noted, in order to transform an inner sterile surface into an outer surface.

In the manner well known in the art, preformed sterile spouts can be fed by means of a vibratory feeder to an indexing head which in turn properly positions the spouts 14, upon the sheets. The sheets can be fixed in position between the indexing head and spout sealing apparatus, by raising a movable table 15 and thus pressing the upper surface of the sheets against the bottom of the spout. A cluster of knives 16 are positioned on the upper surface of the heated dies 17. The upward motion of the heated dies 17 first cuts the film by means of a cluster of knives 16 and then heat seals the spout to the sheets. As shown in FIGURE 1, by means of the use of pairs of vibratory feeders, indexing heads and heated dies, two spouts be simultaneously secured to the sheets thus doubling the number of spouts attached during the spout attaching cycle. The sp outs are advantageously capped, in order to permit the formed bags to be completely sealed. The caps can be automatically removed and replaced during filling operation.

A pair of sheets is fed from a roller 11, to the heat sealing apparatus. Similarly to the sheets from rollers 10, a reversing operation such as see-n in FIGURE 2, can be employed in order to provide a pair of sheets with a sterile upper surface 13.

The sheets from roller 11 are sealed to the spouted sheets from roller 10, by means of a sealing die apparatus 18 which simultaneously forms two spouted bags by heat sealing the four sheets together, in two annular patterns, and the two bags are separated from each other and from the remaining portions of the sheets by means of knives, hot wires, or the like, not shown. The annular pattern of the seals determines the peripheral configuration of the bags. A rectangular pattern is most conveniently employed, in which the two sides of the rectangle correspond to the two edges of the continuous sheet.

A sterile environment must be maintained during periods in which the sterile surfaces of the sheets are exposed to the atmosphere. Accordingly, the sanitary control must be maintained during the steps of unrolling and reversing the sheets, spout attaching and heat sealing the sheets to form a bag. If the spouted sheets and the sheets from roller 11 are brought into firm contact prior to the sealing operation it is possible to eliminate the sanitary control during the latter step.

The formed bags, can advantageously, pass over an inspection member 19, such as light box inspection table of the type well known in the art, in order to permit convenient inspection of the peripheral seals and the spout. The formed bags can be filled in automatic equipment in which sanitary conditions are rigidly maintained.

The present invention is thus seen to provide a process for the manufacture of sheets with the degree of sterility required in the packaging of food products which process does not require sanitary control during the manufacture or storage of the sheets. Rigid control of the sanitation is limited to the steps of inverting the sheets (as seen in FIGURES 2 and 3) and the bag making operation.

The present system also provides a convenient method for attaching spouts to double wall bags which lends itself to a simple, automating operation during which sanitary control can conveniently be maintained.

Although the invention has been described in its preferred forms with a certain degree of particularity, it is understood that the present disclosure of the preferred forms has been made only by way of example and that numerous changes in the details of construction and the combination and arrangements of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.

What is claimed is:

1. The process of forming sanitary double wall bags comprising the steps of forming a plurality of pairs of contiguous sheets, each of said sheets having an outer surface and an inner, sterile surface in contact with an inner, sterile surface of a contiguous sheet, within a sterile environment withdrawing each of said sheets from contact with the sheet with which it is contiguous, and bringing the outer surface of at least one sheet in each of said pairs of sheets in contact with a surface of another sheet to form at least two pairs of contiguous sheets, each of said pairs of sheets having an outer sterile surface, bringing the outer sterile surface of one pair of sheets into contact with an outer sterile surface of another pair of sheets and sealing together the peripheral edges of said one pair of sheets to said another pair of sheets, thereby forming a double wall bag having a sterile interior zone.

2. The process of forming sanitary double wall plastic film bags comprising the steps of forming a plurality of pairs of contiguous sheets, each of said sheets having an outer surface and an inner, sterile surface in contact with an inner, sterile surface of a contiguous sheet, within a sterile environment withdrawing each said sheet from contact with the sheet with which it is contiguous, bringing the outer surface of at least one sheet in each of said pairs of sheets in contact with a surface of another sheet to form at least two pairs of contiguous sheets, each of said pairs of sheets having an outer sterile surface, and passing at least one of said pairs of sheets through a spout attaching Zone, bringing the outer sterile surface of a spouted pair of sheets into contact with an outer sterile surface of another pair of sheets and heat sealing the peripheral edges of said spouted pair of sheets and said another pair of sheets, thereby forming a double wall spouted bag having a sterile interior zone.

3. The process of forming sanitary double wall, plastic film bags comprising the steps of continuously melt extruding a plurality of seamless tubings, continuously withdrawing each of the tubings from the point of extrusion, flattening each of the tubings at a point spaced from the point of extrusion, initiating and maintaining an isolated bubble of a gaseous medium in the section of each of the tubings between the point of extrusion and the point of flattening, continuously withdrawing each of the tubings from said point of flattening, cutting the opposing edges of each of the flattened tubings to form a plurality of pairs of contiguous flat sheets, each of said sheets having an outer surface and an inner, sterile surface in contact with an inner, sterile surface of a contiguous sheet, within a sterile environment withdrawing each of said sheets from contact with the sheet with which it is contiguous, bringing the outer surface of at least one sheet in each of said pairs of sheets in contact with a surface of another sheet to form at least two pairs of contiguous sheets, each of said pairs of sheets having :an outer sterile surface, and passing at least one of said pairs of sheets through a spout attaching zone, bringing the outer sterile surface of 1a spouted pair of sheets into contact with an outer sterile surface of another pair of sheets and heat sealing the peripheral edges of said spouted pair of sheets and said another pair of sheets, thereby forming a double wall spouted bag having a sterile interior zone.

4. The process of claim 2, wherein at least one of the sheets withdrawn from contact with sheet with which it is contiguous, is reversed and the outer surface of the reversed sheet is brought into contact with the outer surface of the sheet from which it was withdrawn from contact.

5. The process of claim 1 wherein at least one of the sheets withdrawn from contact with sheet with which it is contiguous, is reversed and the outer surface of the reversed sheet is brought into contact with the outer surface of the sheet from which it was withdrawn from contact.

6. The process of claim 3, wherein at least one of the sheets withdrawn from contact with sheet with which it is contiguous, is reversed and the outer surface of the reversed sheet is brought into contact with the outer surface of the sheet from which it was withdrawn from contact.

No references cited.

EARL M. BERGERT, Primary Examiner.

D. J. DRUMMOND, Assistant Examiner. 

1. THE PROCESS OF FORMING SANITARY DOUBLE WALL BAGS COMPRISING THE STEPS OF FORMING A PLURALITY OF PAIRS OF CONTIGUOUS SHEETS, EACH OF SAID SHEETS HAVING AN OUTER SURFACE AND AN INNER, STERILE SURFACE IN CONTACT WITH AN INNER, STERILE SURFACE OF A CONTIGUOUS SHEET, WITHIN A STERILE ENVIRONMENT WITHDRAWING EACH O SAID SHEETS FROM CONTACT WITH THE SHEET WITH WHICH IT IS CONTIGUOUS, AND BRINGING THE OUTER SURFACE OF AT LEAST ONE SHEET IN EACH OF SAID PAIRS OF SHEETS IN CONTACT WITH A SURFACE OF ANOTHER SHEET TO FORM AT LEAST TWO PAIRS OF CONTINUGOUS SHEETS, EACH OF SAID PAIRS OF SHEETS HAVING AN OUTER STERILE SURFACE, BRINGING THE OUTER STERILE SURFACE OF ONE PAIR OF SHEETS INTO CONTACT WITH AN OUTER STERILE SURFACE OF ANOTHER PAIR OF SHEETS AND SEALING TOGETHER THE PERIPHERAL EDGES OF SAID ONE PAIR OF SHEETS TO SAID ANOTHER PAIR OF SHEETS, THEREBY FORMING A DOUBLE WALL BAG HAVING A STERILE INTERIOR ZONE. 